| Abstract: | The ultrastructural modifications produced by anisotonic NaCl treatment of Chinese hamster mitotic cells were observed at three NaCl concentrations which have been frequently used in radiosensitization studies: 0.05, 0.5 and 1.5 M. After exposure to 0.05 M NaCl, many well-spread chromosomes are visible. The chromatin fibres are well dispersed and membraneous material is associated with the chromosomes. After hypertonic treatment with 0.5 M NaCl, the chromosomes have a uniform, structureless appearance with some coalescing into larger anaphase-like masses. At 1.5 M NaCl, large scale cellular dehydration is apparent, and filamentous structures such as microfilaments are tightly constricted. The degree of chromosome staining is also reduced below the level of the cytoplasm. After both hypo- and hypertonic NaCl treatment the chromosomes appear swollen relative to untreated cells, but hypertonic treatment causes chromosome clumping and dissociates chromatin. Conformational changes in the chromatin may restrict the capacity for DNA repair and be related to cellular radiosensitivity. |
